The following technologies are known with respect to an imaging device having a continuous photographing function. That is, the imaging device stores output data from an imaging element in a buffer memory once, performs a compression process or the like to the data, and stores the data in the buffer memory again. After that, the imaging device writes the data stored in the buffer memory into a removable recording medium or the like. Such technology is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-199328, Japanese Patent Application Laid-Open No. 2003-87619, and Japanese Patent Application Laid-Open No. HEI03 (1991)-252282.
The imaging device described in the Japanese Patent Application Laid-Open No. 2002-199328 has a first process function to store output data of a photographing element in a first memory area and a second process function to perform a compression process to the data stored in the first memory area and store the data in a second memory area. This imaging device has a recording medium for storing the data stored in the second memory area. This imaging device checks whether a capacity of an empty area in the second memory area is greater than a volume of data after the process in order to prevent the image data after the compression process stored in the second memory area from being overwritten with the newly processed image data. When the empty area has insufficient capacity to store the data after the process, the imaging device stops the writing of data into the second memory area. The imaging device writes the data to be stored in the second memory area into the recording medium to secure the empty area in the second memory area. After that, the imaging device starts the compression process of the image data that is written into the second memory area.
The imaging device which has a RAW buffer area for non-processed image data, a compressed image buffer area for the processed image data, and a recording medium is disclosed in the Japanese Patent Application Laid-Open No. 0.2003-87619. This imaging device checks whether a compressed image buffer is full or not after performing the compression process of the data in the RAW buffer. When the compressed image buffer is full, the imaging device stops the writing into the buffer. The imaging device writes the compressed image data stored in the buffer into the recording medium from the oldest data. The imaging device resumes the compression process or the like that has been interrupted when the capacity of the empty area is secured in the compressed image buffer.
A camera is disclosed in Japanese Patent Application Laid-Open No. 2007-221214 which operates as follows. A control circuit of this camera writes a photographed digital image to which no, process has been performed into a buffer memory and simultaneously performs a process to the digital image. The control circuit reads out the processed digital image from the buffer memory and writes it into a permanent memory. The control circuit determines a processing time of the non-processed image in the buffer memory that are continuously photographed and calculates a continuous photographing speed at which the continuous photographing can be performed at a constant interval in advance. When the control circuit detects that the amount of the image data will reach the almost maximum storage capacity of the buffer memory which stores the non-processed image, it switches the photographing speed to the calculated photographing speed at which the continuous photographing can be performed at a constant interval.